Instruments

Every USCRN observing station is equipped with a standard set of
sensors, a data logger, and a satellite communications transmitter.
Some of the measured parameters (e.g. temperature, precipitation, and
soil conditions) have multiple sensors for redundancy and independent
validation. Off-the-shelf commercial equipment and sensors are
selected based on performance, durability, and cost.

Temperature sensors are placed on a typical 3 meter (10 ft.)
instrument tower at 1.5 meters above the ground surface. Locations
which experience high snowfall and snow depth are given special
consideration. The instrument system is designed to accommodate
additional sensors on the tower without disrupting the physical site.

Hourly and sub-hourly values are stored in a data logger attached
to the tower. A geostationary satellite transmitter sends the data to the
National Centers for Environmental Information where the data undergo a quality control
check and are placed on the Web continuously as the data arrive.

Highly accurate measurements and reliable reporting are
critical. Instruments are calibrated or verified annually, and
maintenance includes routine replacement of aging sensors. The
performance of each station's measurements is monitored on a daily
basis and problems are addressed as quickly as possible, typically
within days.

Stations are powered by a 12-volt battery bank sized by location
with a charging method designed to run the station for several days.
The battery system is charged using a combination of AC, solar,
and/or methanol fuel cells (mainly in AK).